In order to perform a surgical procedure on a target structure of a patient, such as when accessing bony structures, including hips or proximal femurs and vertebral regions, in a patient's body, it is often necessary or at least desirable to dilate the tissue to provide access to the target structure.
One method of providing access to a target structure is to form an incision through the skin and the tissue located between the skin and the target structure and retracting the cut tissue to form an access area. Cutting the tissue is very traumatic to the tissue and is associated with prolonged recovery times and substantial patient discomfort.
Another method of dilating tissue in connection with such procedures employs dilating tissue using multiple separate cannula dilators. Typically, a set of dilators having different diameters will be used. For example, a first dilator of a relatively small outer diameter will be inserted through an incision formed in the patient's skin toward a target structure. A second cannula having an inner diameter substantially equal to the outer diameter of the first dilator will be placed over the first dilator. A third cannula having an inner diameter substantially equal to the outer diameter of the second cannula will be placed over the second cannula. This stepwise dilation of tissue proceeds until an adequate access path is provided to the target structure. This method may be understood to be similar to blunt dissection of the tissue, and may result in less trauma to the tissue and less discomfort to the patient compared to cutting the tissue. However, this method requires substantial amounts of time in terms of requiring serial steps of dilating the tissue and poses significant risks in terms of increased possibilities that the dilators may be misplaced, unorganized, become contaminated, such as by being dropped in an operating room, and the like.
Fusion of two adjacent vertebrae is a common surgical treatment for back injuries due to damage or defects in a spinal disc between two adjacent vertebrae, such as conditions due to a herniated disc or disc degeneration. The entire disc may be removed by a discectomy procedure, and may be replaced with bone or a bone substitute and/or a cage in order to prevent collapse of the disc space between the adjacent vertebrae. Early techniques for stabilizing the adjacent vertebrae included application of a plate or a rod in conjunction with screws across the adjacent vertebrae, after which the adjacent vertebrae would eventually fuse together. Other stabilizing procedures or techniques may include laminectomies, laminotomies, and foraminotomies, among others. However, such techniques commonly required prolonged periods of recovery from the extensive surgery involved.
Bone fixation devices are known that are useful for connecting two or more bone segments for the healing of broken bones, typically including an elongate pin with a distal anchor and a proximal anchor movable on the pin to accommodate different bone dimensions, and to permit tensioning of the bone segments together. A surgical procedure of attaching two or more parts of a bone with a pin-like device may be performed by making an initial incision into the tissue down to the bone, and drilling a hole through the bone parts to be joined. Such bone fixation devices can be useful for fusion of vertebrae together, because such bone fixation devices can be used to join adjacent bone segments through a single percutaneous incision or puncture, without the need to expose any other side of the bone segments to be joined. In either type of procedure, that is procedures for stabilizing vertebrae using plates and rods or bone anchors, there is substantial trauma to the surrounding tissue if a large incision is required.
Thus, there remains a need for tissue dilation systems that are easy to use and do not substantially damage tissue that has been dilated.